204 



THE CEREALS IN AMERICA 



276. Influence of Temperature. — It is the temperature during 

 the maize growing months of May to September inclusive, 

 rather than the average annual temperature, that influences the 

 production of maize. It is not only the temperature of air and 

 soil as expressed by the thermometer, but also the sunshine, the 

 influence of which is not fully expressed by thermometric read- 

 ings. Brewer^ has shown that fifty-five per cent of the maizis 

 crop of 1879 in the United States was grown between July 



isotherms 75° and 

 80° F. and thirty 

 three per cent be 

 tween 70° and 75" 

 F., making a total 

 of eighty-eight pe r 

 cent between July- 

 isotherms 70° F 

 to 80° F. 



It is diflicult h > 



give precise limits to an influence which is one of several abso 

 lutely necessary. Beale ^ has compared the yield of maize witl. 

 the temperature in each of the nine leading maize producing 

 States, viz., Ohio, Indiana, Kentucky, Tennessee, Illinois, Iowa, 

 Missouri, Nebraska and Kansas, during the five months May 

 to September inclusive for sixteen years. No relation in these 

 favored States could be traced between yield per acre and 

 temperature. 



Temperature is well known to influence maturity and maj' 

 thus, indirectly at least, affect yield of merchantable grain, 

 especially in regions near the northern limit of successful cul- 

 ture. The New York State Station ^ compares the soil tempei • 

 ature with yield in crops of different maturity, as follows : 



1 Tenth Census U. S., Vol. Agr. 



2 H. G. Beale: Thesis, B. S. Degree. Ohio State University, 1902. 

 *» N. Y. Rpt. (Geneva) 1886, p. 39. 



Map showing area tn Northern Hemisphere between July iso- 

 therms, 70'' and 80° F., indicating suitable temperature for 

 the production of maize. Note rainfall in chart (27 5). 



